Air flow plate grinders



Jam 8, 1957 c. UscHMANN 2,776,800

AIR FLOW PLATE GRNDERS Filed June 27, 1952 4 Sheets-Sheet 2 ,4 Trae/Vro" Jan. 8, 1957 c. UscHMANN 2,776,800

AIR FLOW PLATE GRNDERS Filed June 27, 1952 4 Sheets-Sheet 3 o Z7 o o u Y A' AJZ7 ,Il INVENTOR. o D o o @war usw/MANN a 0 @Vaag M 1m Jan. 8, 1957 c. uscHMANN 2,776,800

AIR FLOW PLATE GRINDERS Filed June 27, 1952 4 Sheets-Sheet 4 INVENTOR.

- (fuer afm/MANN BY W'MX ZAM United States Patent AIR rrow PLATE GRINDERS 'Curt Uschrnann, Lebanon, Orcg., assigner to Cascades Plywood Corporation, Portland, Oreg., a corporation of Delaware Application .lune 27, 1952, Serial No. 295,961

6 Claims. (Cl. 241--296) The present invention concerns a plate type of grinder, the action of which is to shred material iinely or to defiber material of fibrous character such as wood, cornstalks, bagasse, etc. Such grinder thus tears the material into fibers rather than pulverizing it into dust.

An important object accomplished by the present grinder is to afford a large grinding capacity for reducing wood chips or small pieces of other fibrous material to tine, woolly consistency. It is an incidental object to provide a structure which will produce shorter or longer fibers as may be desired.

A further object is to provide such a grinder which will create a strong current of air through it for the purpose of expediting passage between the grinding plates of material to be ground, so that not only will the capacity of the grinder be high, but the material can be reduced to ne fibers without danger of them being burned because of the cooling elfect of the air current between the grinding plates. The fire hazard also is consequently reduced, and the life of the grinding plate ribs or serrations is increased.

By adjusting the spacing between the plates constituting the grinding surfaces the neness of the bers can be regulated, and the plate adjusting mechanism can be calibrated to enable the grinder to be adjusted in predetermined fashion with ease.

It is desired that the grinder be capable of delibering material varying widely in moisture content, so that either dry or wet material may be ground properly and expeditiously.

An advantage of the grinder is that while it is of rugged construction it is simple and has few parts so that the initial cost is low, and it will require very little maintenance.

The chamber in which the grinding plates are located has its outer periphery shaped concave axially to enable the air llow to sweep such 'chamber clean of fibrous material so that it will not accumulate in pockets or corners.

The grinder incorporates two circular plates having ribbed or serrated adjacent faces, at least one of which is mounted for rotation, so as to effect relative rotation between such plates. Conventional driving mechanism, for example an electric motor, may be connected to turn one of the plates while the other is held stationary. The ribbed or serrated surfaces of the plates are generally parallel, preferably being flat, and such plates are located close together so that material passing between the plates is torn or shredded by interaction of the ribs on them. While these ribs extend generally radially, ribs in an annular row located near the periphery of each plate preferably are inclined in one direction relative to radii of the plates, and additional ribs preferably are arranged in an adjacent annular row and inclined in the opposite direction relative to radii of the plates. The length of the ribs in the outer annular row governs the fiber length, and if the ribs in the outer row are short, the average ber length will be shorter than the average length of fiber produced by grinding plates in which the ribs in the outer annular row are longer.

Patented Jan. 8, 1957 Encircling the peripheries of these disks is an annular suction chamber from which air is ejected by rotary fan blades preferably integral with or mounted on the rotating grinder plate, so that air will be drawn through the space between the relatively rotating plates from the supply aperture for the material to be ground, and sup plemental air may be admitted through an auxiliary inlet port by-passing the grinding space between the plates if desired. The blades may extend radially yof the rotary plate and be on its side opposite its grinding or serrated surface.

Provision may be made for adjusting the stationary plate axially toward and away from the rotary plate to vary the spacing between them.

The drawings illustrate a preferred type of grinder construction, but various details may be altered without departing from the principles responsible for the improvement in capacity and perfonnance achieved by this grinder.

Figure l is a side elevation view of a grinder installation with parts broken away, and Figure 2 is a vertical sectional view through the grinder taken on line 2-2 of Figure l. l

Figure 3 is a horizontal section through the grinder with parts successively broken away to show internal grinder structure.

Figure 4 is an enlarged vertical sectional View through a portion of the grinder showing details of plate installation, and Figure 5 is a plan View of a plate section.

Figure 6 is a top perspective view of one end of a plate section showing the grinding ribs more clearly; Figure 7 is a plan view of a fragment of a plate section showing one type'of rib structure; and Figure 8 is a corresponding view of a plate section fragment showing another type of rib formation.

Figure l9 is a bottom perspective view of the rotary plate without the grinding plate sections mounted on it, and showing the impeller vanes or blades.

While the particular features of the present invention are concerned with the grinding plates, the suction charnber in which these plates are mounted and the impeller for creating the air flow through the chamber, a typical grinder installation has been illustrated in the drawings to indicate a representative embodiment of the invention. Thus in Figure l the grinder may be carried by a stand 1, through which a shaft 10 extends vertically. On this shaft a number 4of pulleys 11 are mounted to be driven by V-belts 12, which in turn are driven by corresponding pulleys 13 secured upon the shaft 14 of a motor 15. The grinder base may be anchored to a mounting beam 16 on which is also supported a motor mount 17 slidable along the beam. An adjustable anchor 18 for the motor mount can be regulated to move the motor mount toward or away from grinder stand 1, so as to place the V-belts 12 under the proper tension.

In an installation such as depicted in Figure l the Igrinding surfaces of the disks or plates mounted on holders 2 and 20, as shown in Figure 2, Will be disposed in closely spaced, parallel, horizontal planes. lt is preferred that the upper grinding plate holder 2 be supported stationarily from the grinder housing 21 except as it may be adjustable vertically closer to or farther from plate holder 2t). This lower plate holder is mounted on the upper end of shaft 10, which is journaled in the stand 1 in suitable radial and thrust bearings.

While the disk holder 2 is carried by the grinder housing 21, it is preferably mounted directly upon a cap piece 22 for the housing, which is threadedly connected to a mounting ring 23. Such ring fits in an aperture in the upper side of housing 21 and is secured in place by bolts spaced circumferentially around it. Vertical adjustment of the upper plate holder 2 andcap piece 22 may be effected by turning hand wheel 24 to rotate a pinion 25 which meshes with gear teeth 26 formed on the periphery of the cap piece. lf desired, the circumference of this .cap Apiece may be vgraduated with reference to the pitch of the threads interconnecting the cap piece and its mounting ringso that the axial movement of plate holder 2 for .a given rotation of the cap piece relative to an in- .dicating pointer 26' will be designated. Rotation of cap `piece 22 in the direction of rotation of the plate holder 20 'will raise plate holder 2, so that the grinding7 plates will tend to .beseparated if their ribs strike.

It .is preferred `that the grinding .ribs carried by holders 2 and 20 be formed integrally on plates mounted on such holders. Such plates may be formed of removable ribbed plate sections 3 and 30, secured respectively to the holders 2 and 20. Each section 13 may have apertures 31 through it, three such apertures being shown in Figure 5, `to re- .ceive anchor vbolts 32 for securing the plate sections to .the holders. Each section lpreferably extends about a Vminorportion -of the circumference .of its holder, that in Figure forming one-sixth of the total grinding surface. The grinding element for each holder may thus be divided into four, six, or eight sections, for example, and if the holes 31 are slightly elongated radially, as shown in Figure 5., the sections may all be pushed firmly toward the center to abut reference surfaces at their circumferential ends for `locating the sections in uniform posi- -tion radially of the axis of rotation. Sections 30 are similarly secured to the rotating holder 20 by bolts 33.

The vgrinding rib structure of preferred form is shown best in Figure 6. It includes a raidall-y inner row of relatively .coarse ribs 34 Vto withstand the heavy load produced by chips of wood, for example, passing between them. Next radially outward from the ribs 34 is a row of liner ribs 35 which latter ribs are closer together and have Vshallower grooves between them. Both the ribs 34 .and the ribs 35 may .extend directly radially as shown in Figures 5, 7 and 8.

Radially outwardly lfrom the row of ribs 35 are two rows of inclined ribs. The ribs 36 in the inner row are inclined outwardly in the `direction of rotation relative to the `respective radii .passing through such ribs, while the ribs 37 in end-abutting relationship to the ribs 36 are inclined radially outwardly opposite to the direction of rotation. The `ribs on the stationary plate sections will be the `mirror image of the ribs on plate sections 30 shown -in Figure 3, and the inclined arrangement of the ribs affords a shearing action. Both the ribs 36 and the ribs 37, as shown in Figure 6, are of substantially triangular transverse cross section, forming substantially sharp ridges, and defining between them grooves of substantially triangular cross section open at both ends.

On the underside of the rotary plate holder 20 are fan 'blades or impeller vanes 27, shown best in Figures 4 and 9, extending generally radially of the plate holder and which may extend precisely radially of 'the plate holder. V-If the vanes are thus symmetrically arranged, the plate holder may be turned in either direction because the housing 21 likewise is `symmetrical about a vertical plane as 'shown in Figure 3, being of generally circular cross section in planes perpendicular to the axis of rotation of the 'plateiholder 20. Such vanes preferably are planar. The `numberof `such blades is not critical, but several of them should be provided, six being shown in the drawings.

The chamber 28 encircling the grinding disks 3 and 30 within the casing 21 is -of a depth or axial extent at least several times as great as the spacing between the peripheries of plates 3 and 30 and considerably greater than the over-all depth of the rotating plate between its grinding `surface and theextreme opposite edges of vanes 27. This chamber is of substantially semicircular cross section with its outer wall .concave axially so as to avoid the formation of corners which would create `dead spots, eddies or tur 'bulencein the air flow.

As rthe vanes 27 move through the chamber 28 .during rotation of plate 30 they will drive the air from the chamber 28 toward the large outlet duct 29 irrespective of the direction in which the plate 30 is turned. Such outiiow through the outlet duct will produce a suction in chamber 28 inducing a flow of air between the relatively rotating disks 3 and 30 from their centers toward their peripheries. Air will be supplied to the center of these disks through the supply opening 4 concentric with shaft 10. Thus a strong .air tiow is effected between the grinding surfaces assisting the centrifugal force generated by relative rotation of the plates to move the stock being ground from the inlet 4 to the outlet 29.

As the chips of wood are drawn between the grinding plates they may be oriented in any direction at first. Usually the chips will be more or less at and consequently will tend to move edgewise through the space between the grinding disks. Because the ribs 34 and 35 extend radially of these .plates the chips will tend to be oriented with their fibers progressively nearer parallelism with the ribs. Instead of the ribs then bending or chopping the chips across their fibers the grain fibers of the pieces will tend to be pulled apart.

Moved by the air stream and by centrifugal force, the fiber bundles will progress radially outward toward the periphery of the plates along the inclined ribs 36 from the ribs 35. To pass from the ribs 36 tothe ribs 37 the fibers tend to bend. lt has been found that the length of the ribs 37 will affect the average fiber length. These ribs, as shown in Figure 7, arc shorter than the ribs 37 in Figure 8, .and the fibers produced by disks ribbed as shown in Figure 7 will be shorter than the fibers produced by plates ribbed as shown in Figure 8 on the average. In each instance, however, the intermediate ribs 36 are a plurality of times as long, in fact several times as long, as the outer ribs 37 or 37. While the ribs 37 of Figure 8 are longer Athan the ribs 37 of Figure 7, the ribs 35 and the ribs 34', respectively, will be shorter than the ribs 35 and 34 of Figure 7.

The thickness or coarseness of theiibels produced by the grinder will be determined by the proximity of the ribs on -the upper and lower grinding plates 3 and 30. The closer the ribbed surfaces are located, the finer will .be the bers. As explained previously, the spacing of plates 3 and 30 may be adjusted by rotation of wheel 24 to a very tine degree. When the upper plate has been adjusted to the proper spacing from the lower plate, it may -be locked in `position by securing wheel 24 in any suitable manner, or by locking gear 26 or pinion 25 in .any suitable fashion.

The volume of air liowing through the grinding space between plates 3 and 30 from the supply aperture 4 to the suction chamber 28 may be regulated by supplying air directly to the suction chamber through the wall of casing 21 if desired. Moreover, by such expedient the circum ferential flow of air through the suction chamber 28 may be preserved. For this purpose ports 4), closable by cov- .ers 41, may be spaced circumferentially around casing 21 as shown in Figure 3. In this instance the cover has been removed from the port 40 at the left of the figure -to admit supplemental air through it into the suction chamber, which would decrease the suction air flow between plates 3 and 30 to the extent that air is supplied through the port 40. Two or all thrce of these ports may similarly be opened. When closed, the inner faces of -covers l4l are shaped completnentally to the peripheral surface of the suction chamber 28 so that a continuous and uniform wall is formed about the grinder.

The structure of the grinder is such as to facilitate servicing. To examine or to remove and replace grinder plate sections, the bolts securing ring 23 in place on the housing 21 may be removed, and the bolt holding the assembly `of wheel 24 may be taken out. Thereupon the entire cap piece 22, plate holder 2 and grinding plate sections 3 .may -be ylifted out .of the grinder as a unit and inverted to expose the grinder sections 3. At the same time the grinding sections 30 on plate holder 20 are exposed to view, and the entire assembly on plate holder` 20 may be disassembled as a unit merely by removing nut from the upper end of shaft 10.

' I claim as my invention: Y

l. Grinding apparatus comprising a housing of generally circular cross section, a pair of cooperating grinding plates received in said housing being of a diameter substantially smaller than the maximum internal diameter of said housing and having adjacent serrated grinding surfaces, means driving one of said plates for rotation relative to the other of said plates, said rotatable plate having generally radially extending blower vanes projecting axially from the side thereof opposite the other grinding plate, said housing having an air circulation chamber outwardly of said plates and vanes of substantially semicircular cross section with its outer wall concave axially, and means operable to guide air and material to be ground into the space between said grinding plates, said housing air circulation chamber having a peripheral discharge opening through which said vanes may discharge air drawn into the space between said plates and ground material carried thereby.

2. The grinding apparatus dened in claim l, in which the rotatable `plate includes three groups of radiating ribs, including an inner rib group having ribs extending substantially radially and spaced relatively far apart, an intermediate rib -group disposed radially outward from said inner rib group and having ribs spaced closer together than the ribs in said inner rib group and inclined in one direction relative to the ribs of said inner rib group, and an outer rib group, disposed radially outward from said intermediate rib group and having ribs spaced closer together than the ribs of said intermediate rib group and inclined relative to the ribs of said inner rib group in the direction opposite the inclination of the ribs in said intermediate group relative `to the ribs in said inner rib group.

3. Grinding apparatus comprising a housing of generally circular cross section, a pair of cooperating grind* ing plates received in said housing being of a diameter smaller than the maximum internal housing diameter and having adjacent serrated grinding surfaces, means driving one of said plates for rotation relative to the other of said plates, said rotatable plate having generally radially extending blower vanes projecting from the side thereof opposite the other grinding plate, vand means operable to guide air and material to be ground into the space between said grinding plates for passage therethrough, said housing including a chamber encircling the peripheries of said plates and having a peripheral discharge opening through which said vanes may discharge air ydrawn into the space between said plates and ground material carried thereby, and said housing chamber having a second peripheral opening smaller than said discharge opening, spaced circumferentially of the housing therefrom and opening directly into such chamber, through which air is drawn by said blower vanes directly into such housing chamber for supplementing the air discharged from the space between said grinding plates.

4. A grinding disk having thereon three groups of radiating ribs, including an inner rib group having ribs extending generally radially, an intermediate rib group disposed radially outward from said inner rib group and having ribs inclined in one direction relative to the ribs of said inner rib group, and an outer rib group, disposed radially outward from said intermediate ribs group and having ribs of substantially triangulartransverse cross section, forming substantially sharp ridges, inclined relative to the ribs of said inner rib group in the direction opposite the inclination of the ribs in said intermediate group relative to the ribs in said inner rib group, and defining between them grooves flared from their bottoms in transverse cross section. f

5. A grinding disk having thereon three group of radiating ribs, including an inner rib group having ribs extending substantially radially and spaced relatively far apart, an intermediate rib group disposed radially outward from said inner rib group and having ribs spaced closer together than the ribs in said inner rib group and inclined in one direction relative to the ribs of said inner rib group, and an outer rib group, disposed radially outward from said intermediate rib group and having ribs of substantially triangular transverse cross section,

forming substantially sharp ridges, inclined relative to the ribs of said inner rib group in the direction opposite the inclination of the ribs in said intermediate group relative to the ribs in said inner group and spaced closer together than the ribs of said intermediate rib group, dening between them -grooves of substantially triangular transverse cross section substantially open at both ends.

6. A grinding disk having thereon three groups of radiating ribs, including an inner rib group having ribs extending substantially radially, an intermediate rib group disposed radially outward from said inner rib group and having ribs inclined in one direction relative to the ribs of said inner rib group, and an outer rib group, disposed radially outward from said `intermediate rib group and having ribs of substantially triangular transverse cross section, formingV substantially sharp ridges, inclined relative to the ribs of said inner rib group in the direction opposite the inclination of the ribs in said intermediate group relative to the ribs in said inner l`rib group, and deiining between them grooves of substantially triangular transverse cross section' substantially open at both ends.

References Cited in the tile of this patent UNITED STATES PATENTS 

